An electrical discharge (hereinafter “discharge”) may occur in an X-ray tube. If a discharge occurs in an X-ray tube, a power supply to the X-ray tube is immediately shut off to stop X-ray emission. After the atmosphere within the x-ray tube becomes stable, the power supply to the X-ray tube is resumed to restart X-ray emission. The period of stopping X-ray emission by shutting off the power supply to the X-ray tube after a discharge has occurred is from several tens of milliseconds to several hundred milliseconds. During the period of stopping emission, data used to reconstruct an image cannot be acquired, thereby artifacts generate in a reconstructed image. Accordingly, the occurrence of an electrical discharge interferes with diagnosis.